Nitropolis 4

|ELK Studios|2023-02-23|RTP: 94.00 %
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Game provider
ELK Studios
Nitropolis 4
Feature Buy
Game type
Video Slots
Mobile version
Grid slot
Sticky wilds
Free spins
Bonus game
Progressive jackpot
Min. bet
Random Feature
Max. bet
Maximum win
Last update
January 21, 2023


4 votes - 4.00/5.00

Join the furry animal gangs for underwater escapades on the video slot sequel from Elk Studios. Nitropolis 4 pits the chaotic crews across six expanding reels with up to 262,144 ways to pay, further increased into millions of bet ways by the dynamic Nitro Reels. Throw in big symbols up to 4×4, eight random features, Nitro Multipliers, plus a free spins bonus and a super bonus for barking mad wins of up to 50,000 times your bet.

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Slot Details

Nitropolis 4 is a cascading video slot with 6 reels, 4 rows and 4,096 ways to pay as default. The number of rows can extend to 8 per reel, resulting in 262,144 ways to win. Furthermore, millions of bet ways can be reached via the Nitro Reels. Wins are awarded for matching three or more symbols on consecutive reels starting from the leftmost. You can join the abstract animal antics from 0.20 to 50 credits per spin. This game has a high volatility rating and a 94% RTP.

Following the Nitro Gangs escape from Nitropolis to the seaside climate of Nitropolis 3, their latest escapade seems to involve drilling from oil rigs. An industrial EDM track creates a harsh mood with radio soundbites and foreboding chords. The familiar toxic green complements the bright colour set of the dystopian series, and the bonus round takes us underwater on a search for wins in a mini-sub.

Nitropolis 4 Slot Screenshot
Nitropolis 4 Slot – Base Game

The pay symbols start at the low end with J, Q, K and A, awarding 0.3x your stake for six-of-a-kind. They are followed by the gang badge symbols of The Rogue Rats in blue, The Pug Thugs in green, Gritty Kitty in pink, and The Dirty Dawgs in red for the medium pays. Matching six across the reels will pay 0.8x or 1x your bet. The remaining symbols are the rat, pug, kitty and dog in their gang’s colours, and six-of-a-kind awards 1.25x to 3x your stake.

The wild symbol appears as an underwater mine, which substitutes all others except for the bonus and super bonus scatters, plus the Nitro feature symbols, as detailed below. A small submarine represents the bonus symbol that triggers the free spins for landing three or more. A single super bonus sub will upgrade the bonus to the super free spins.

Nitropolis 4 Slot Features

It’s been around eight months since the Nitro Gangs returned for the third instalment on Nitropolis 3, following the original from 2020. The gameplay for each has trumped the previous for impressive combinations of features with eye-catching effects and presentation, leaving this fourth episode impossible to pass without a closer look.

Before diving into the features, there are three basic symbol types that drive the game; standard 1×1 symbols, big symbols of 2×2, 3×3 and 4×4, and Nitro Reels, which span two rows with 4, 6, 8, 10 or 12 1×1 symbols contained, framed in green with the symbol count on display.

Nitropolis 4 Slot Screenshot
Nitropolis 4 Slot – Max Rows & 3×3 Symbol

In addition, the game features 2×3 Big Nitro Reels containing 2, 3, 4, 5 or 6 2×2 big symbols. When calculating pays, big symbols are broken down into 1×1 equivalents, e.g. a 2×2 big symbol equates to four standard 1×1 symbols.

New to the series, Nitro Multipliers can appear in Nitro Reels with x4, x6, x8, x10 or x12 multipliers, which multiply all wins in view. More than one Nitro Multiplier will act multiplicatively, e.g. an x8 and an x10 Nitro Multiplier in view will multiply any wins by x80.

At the heart of each spin is the Avalanche mechanic that cascades symbols onto the default 6×4 grid at the start of a spin sequence. Any wins are paid before they disappear to make room for new and existing symbols to drop and fill the gaps. Space created beneath a big symbol due to an avalanche will be filled with 1×1 symbols of the same type.

With each avalanche, the reels expand with a new row of symbols. The mix of expanding reels and cascading symbols gradually increases the play area from four rows and 4,096 ways up to the maximum height of eight rows and 262,144 ways. The addition of extra symbols from Nitro Reels can further increase the number of ways to pay into millions.

Nitro Reels that form part of a winning combo stay in view and respin a new symbol or Nitro Multiplier with each avalanche sequence. On any non-winning spin, should half a Nitro Reel or a big symbol appear in the top row, the grid will expand, initiating an avalanche of cascading symbols to complete the row. A spin concludes when no new wins occur before it resets back to the standard 6×4 grid for a new spin.

Nitropolis 4 Slot Screenshot
Nitropolis 4 – Super Bonus

Above the reels, two screens represent the Nitro Booster that can add features to each spin at random. All features trigger for the ensuing spin except for the Redrop feature. There are eight features in total:

  • Redrop: Following any wins or avalanches, this feature removes all symbols before dropping a new set, except for Nitro Reels, wild and bonus symbols.
  • Both Ways: Pays both ways from left to right and right to left.
  • Max Rows: Expands the reels up to the maximum height of eight rows.
  • Garbage Collect: Randomly selects one symbol type to be removed, initiating an avalanche.
  • Nitro Appear: Replaces existing symbols with a Nitro Reel.
  • Nitro Wild: Fills an existing Nitro Reel with wild symbols.
  • Nitro Upgrade: Upgrades an existing Nitro Reel, e.g. a Nitro Reel with a symbol count of 4, may be upgraded to a 6, 8, 10 or 12 symbol count.
  • Nitro Match: An existing Nitro Reel is matched to contain a selected symbol from an adjacent reel.

Land three or more bonus scatters to trigger the Nitropolis 4 Free Spins. Three, four, five or six bonus symbols award 8, 12, 16 and 20 free spins, respectively. During free spins, for every free spin that results in a win, a Safety Level is enforced, adding an extra row to the reels. Each new free spin starts at the currently active Safety Level. In addition, all Nitro Reels that land will stay in play until the end of the bonus.

Furthermore, landing a super bonus scatter as part of the scatter combination will trigger the Nitropolis 4 Super Bonus. Super bonus scatters can only appear in a Nitro Reel. The super bonus starts with the Max Rows and Both Ways features active throughout the round, resulting in the maximum format of eight rows, and both ways pays.

Nitropolis 4 Slot Screenshot
Nitropolis 4 Slot – X-iter Feature

As expected, Elk Studios X-iter feature makes a return on Nitropolis 4. X-iter gives players a choice of game modes with modified reels, bonus buys, and more for a fixed increase in stake value. The Nitropolis 4 X-iter feature provides a selection of the five following spin scenarios:

  • Bonus Hunt | 2x Bet: With this mode enabled, the chances of triggering a bonus game naturally are doubled.
  • Nitro Booster | 10x Bet: With Nitro Booster mode enabled, two features are guaranteed when the Nitro Booster is activated.
  • Super Spin | 25x Bet: With Super Spin active, the Max Rows and Both Ways features are guaranteed every time.
  • Bonus | 100x Bet: A bonus triggering spin into the Nitropolis 4 Free Spins.
  • Super Bonus | 500x Bet: A bonus triggering spin of the Nitropolis 4 Super Bonus.

Final Verdict

Nitropolis 3 was by far the greatest evolution of the series, merging the increasing ways effects of the Nitro Reels with the expanding reel set of Elk Studios Gold series. This latest episode further adds to the captivating gameplay with Nitro multipliers and the Garbage Collect feature. Not too far removed from the last, yet with enough diversity to distinguish itself, Nitropolis 4 is a triumph of engaging game design with captivating spin sequences.

The curse of such engagement can often be more razzle than rewarding dazzle, and online slot connoisseurs may sniff at the 94% RTP. Still, it’s hard not to be impressed by the monumental effort in development from the leading studio. Successful drills for wins will feature a combination of Nitro Multipliers, which can elevate six-of-a-kind wins into epic proportions in both the base game and during bonus rounds.


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